The Earth's Core Mantle boundary

The structures and conditions at Earth's core-mantle boundary (CMB) influence many global functions, such as the geodynamo and overall global heat flow. The nature of the boundary, in particular the core-side of the CMB, is still largely unknown. Many studies have hypothesized that there may be thin layer(s) at the top of the liquid core. One way to determine if they exist is the examination of seismic wave velocities passing through the shallowest parts of the core. To this end, we developed a novel way of applying Wiener Deconvolution, called Empirical Transer Functions, to SmKS  teleseismic core phases (Alexandrakis and Eaton, 2007). This new method removes the noise and data scatter caused by lower mantle velocity heterogeneities, such as the D''.

Careful selection of SmKS phases produced a dataset with a fairly uniform global coverage, resulting in a globally averaged 1D velocity model, AE09, for the outer 200km of the CMB (Alexandrakis and Eaton, 2010). Model AE05 fit the observed SmKS traveltimes better than the standard Earth models AK135, IASP91 and PREM.

Regional studies, such as an analysis of outermost core velocities under the Pacific Ocean or polar regions, could show local velocity heterogeneities which are not apparent in the globally averaged model AE09.

Contact: Catherine Alexandrakis


Peer-reviewed Publications

Alexandrakis, C., D. W. Eaton, 2007, Empirical transfer functions: Application to  determination of outermost core velocity structure using SmKS phases. Geophysical Research Letters, 34, L22317, doi: 10.1029/2007GL031932.

Alexandrakis, C., D. W. Eaton, 2010. Precise seismic-wave velocity atop Earth's core: No evidence for outer-core stratification. Physics of the Earth and Plantery Interiors, 180, 59-65, doi: 10.1016/j.pepi.2010.02.011


Alexandrakis, C., 2011. Teleseismic array studies of Earth's core-mantle boundray. PhD Thesis, University of Calgary.

Mueller, R. M. 2018. Investigating Core-Mantle Boundary Velocities below the Pacific Ocean. Bachelor Thesis, TU Bergakademie Freiberg